Chapter 12.2, Problem 68AYU

Make up an arithmetic sequence. Give it to a friend and ask for its 20th term.

To determine

To find: Make up an arithmetic sequence. Give it to a friend and ask for its 20th term.

Answer to Problem 68AYU

$a_{20}=-92$

Explanation of Solution

Given:

Consider an arithmetic sequence

$3,-2,-7,-12\dots$

Formula used:

If first term $a_1$, and common difference $d$ are known then nth term of the sequence is,

$a_n=a_1+\left(n-1\right)d$

Calculation:

From the given arithmetic sequence,

$a_1=\text{ 3},d=-5$ and $n=20$.

$a_{20}=3+\left(20-1\right)\left(-5\right)$

$=3-95=-92$

$a_{20}=-92$